挖一条水渠，第一天挖了全长的24%，第二天挖了全长的16%，还剩下420m，这条水渠长多少米？
\u6316\u4e00\u6761\u6c34\u6e20\uff0c\u7b2c\u4e00\u5929\u6316\u4e86\u5168\u957f\u768424%\uff0c\u7b2c\u4e8c\u5929\u6316\u4e86\u5168\u957f\u768416%\uff0c\u8fd8\u5269\u4e0b420m\uff0c\u8fd9\u6761\u6c34\u6e20\u957f\u591a\u5c11\u7c73?\u6316\u4e00\u6761\u6c34\u6e20\uff0c\u7b2c\u4e00\u5929\u6316\u4e86\u5168\u957f\u768428%\uff0c\u7b2c\u4e8c\u5929\u6316\u4e86\u5168\u957f\u768430%\uff0c\u4e24\u5929\u540e\u8fd8\u5269\u4e0b2100\u7c73\uff0c\u8fd9\u6761\u6c34\u6e20\u957f\u591a\u5c11\u7c73\uff1f
\u5168\u957f\u4e3a\uff1a
2100\u00f7(1-28%-30%)
=2100\u00f742%
=5000(\u7c73)
\u6765\u81ea\u7f51\u7edc
\u7b2c\u4e00\u5929\u6bd4\u7b2c\u4e8c\u5929\u5c11\u6316\u4e86\u5168\u957f\u768424%-16%=8%\uff0c\u7b2c\u4e00\u5929\u6bd4\u7b2c\u4e8c\u5929\u5c11\u6316\u4e86200\u7c73\u3002
200/(24%-16%)=2500\u7c73
=420÷60%
=700米
420/(1-0.24-0.16)=420*5/3=140*5=700mi
绛旓細绗竴澶╂寲浜嗗叏闀2/5,涔熷氨鏄400*2/5=160绫,鍓╀綑240绫 绗簩澶╂寲浜嗗墿浣欑殑3/5,涔熷氨鏄240*3/5=144绫 绗笁澶╂寲瀹,鎵浠ョ涓夊ぉ鎸栦簡400-160-144=96绫
绛旓細璁绗竴澶╂寲鐨闀垮害涓篨,鍏ㄩ暱涓篩.鍙垪寮忓涓嬶細X*9/10=50 X绾︾瓑浜55.55 Y*2/9=55.55 Y绾︾瓑浜249.98
绛旓細绗竴澶╂寲浜1/4锛岀浜澶╂寲浜2/5锛岄偅涔堜袱澶╀竴鍏辨寲浜嗭紙1/4+2/5锛夛紳5/20+8/20锛13/20 鏍规嵁璁＄畻鐨勭粨鏋滐紝涓ゅぉ鎸栦簡鍏ㄩ暱鐨65锛咃紝鑰屼袱澶╂寲浜65绫筹紝鎵浠姘存笭鍏ㄩ暱100绫炽
绛旓細鎸栦竴鏉℃按娓,绗竴澶╂寲浜嗗叏闀跨殑4鍒嗕箣1,绗簩澶╂寲浜嗗叏闀跨殑20鍒嗕箣7,涓ゅぉ鍏辨寲浜870m锛岃繖鏉℃按娓犻暱澶氬皯绫筹紵870梅(1/4+7/20)=870梅3/5 =1450绫
绛旓細鏌愬叕鍙告寲浜涓鏉℃按娓,绗竴澶╂寲浜嗗叏闀跨殑浜斿垎涔嬩簩,绗簩澶╂寲浜嗗叏闀跨殑鍏垎涔嬩笁,绗笁澶╂寲浜90绫虫濂藉叏閮ㄥ畬鎴,杩欐潯姘存笭澶氶暱?... 鏌愬叕鍙告寲浜嗕竴鏉℃按娓,绗竴澶╂寲浜嗗叏闀跨殑浜斿垎涔嬩簩,绗簩澶╂寲浜嗗叏闀跨殑鍏垎涔嬩笁,绗笁澶╂寲浜90绫虫濂藉叏閮ㄥ畬鎴,杩欐潯姘存笭澶氶暱? 灞曞紑 鎴戞潵绛 2...
绛旓細6.5梅锛1- 1 6 - 2 5 锛夛紝=6.5梅 13 30 锛=15锛堝崈绫筹級锛庣瓟锛氳繖鏉℃按娓犲叏闀15鍗冪背锛
绛旓細绗竴澶2/5 绗簩澶2/5*7/12=14/60 绗笁澶╂槸1-2/5-14/60=22/60 绗笁澶╂瘮绗簩澶╁鎸22/60-14/60=8/60=2/15 鏄100绫 鎵浠姘存笭涓鍏100/锛2/15锛=750绫 骞冲潎姣忓ぉ鎸750/3=250绫
绛旓細60/(1-0.25-0.75*銆3/7)锛140 濡傛灉浣犳槸涓鐢燂紝瑕佹眰鐢ㄦ柟绋嬫硶锛屽彲浠ヨ繖鏍凤細璁捐繖鏉℃按娓犵殑鍏ㄩ暱涓篨绫 鍒欍1/4X锛(1-1/4)*3/7X锛60锛漍 鎵浠ャ3/7X锛60 鎵浠ャX锛140 绛旓細杩鏉℃按娓犲叏闀鏄140绫
绛旓細4鍙 1/3 闄や互 锛1-1/5-2/5锛=10鍙5/6 锛堢背锛鍏ㄩ暱 10鍙 5/6绫
绛旓細姘存笭闀 (47-7)梅锛1-2/7-1/3锛=40梅锛1-6/21-7/21锛=40梅8/21 =105绫
